The present invention relates to a zoom lens drive mechanism of a camera in which a zooming cam position can be correctively adjusted in an intermediate range of the focal length after the adjustment of focus of the zoom lens for the longest and the shortest focal lengths.
Various compact cameras with zoom lenses of which the focal length can be continuously changeable have become increasingly popular by reason of the convenience of taking pictures of various subjects.
A zoom lens advantageously incorporated in compact cameras consists of a zoom lens system comprising, for example two lens means, and two lens barrels; one is movable axially relative to the camera body and the other is fixed. The movable lens barrel holds the front lens means fixedly therein and the rear lens means movably therein. The focal length of the zoom lens system is changed by either axially shifting or rotating the movable lens barrel relative to the fixed lens barrel to shift the front and rear lens means in a predetermined relationship. In addition to changing the focal length, the movable lens barrel should be otherwise shifted or rotated to focus the zoom lens system. The front and rear lens means are relatively shifted in different relationship between focusing and zooming. This is performed by a coaction of cams provided in the movable and/or fixed lens barrels and cam follower pins attached to lens holders of the front and rear lens means.
Production errors arise when assembling such zoom lenses, and so the lens system is subjected to focus tracking adjustment in order to focus the zoom lens system over the whole range of possible focal lengths thereof. Such a focus tracking adjustment is performed by changing the relative position of the cam follower member to the cam. That is, after the focus tracking adjustment for the longest and the shortest focal lengths or telephotography and wide-angle photography, respectively, the focus tracking adjustment for the intermediate focal length range is carried out by shifting the component lens means stepwise between positions suitable for telephotography and wide-angle photography. But conducting this focus tracking adjustment for the intermediate focal length range often causes a change of focus for telephotography and wide-angle photography. Therefore, such a focus tracking adjustment is quite troublesome.